Current approaches to treat sudden sensorineural hearing loss (SSNHL) do not maintain inner ear drug concentrations within an appropriate therapeutic window for sufficient lengths of time to achieve therapeutic effect. A novel delivery system for long-term, controlled release of glucocorticoid steroids to the inner ear would constitute a dramatic improvement in SSNHL treatment options. Our proposed strategy uses Precision Particle Fabrication (PPF) to create betamethasone-loaded microspheres for transtympanic injection, round window membrane (RWM) localization, and sustained-release to the inner ear. The central advantage of our approach is that PPF technology allows for precise control of particle size, shape, material, and release rates. Our long-term goal is for transtympanic delivery of PPF-enabled betamethasone-loaded microspheres to be the standard-of-care for people who suffer from SSNHL. We hypothesize that microspheres can be retained on the RWM for two weeks and that betamethasone release can be maintained within 25% of a therapeutic dose (~55 ng/day). We expect that this novel approach will enable sustained levels of therapeutic concentrations of betamethasone to the inner ear that will dramatically improve the safety and efficacy of SSNHL treatments over currently available options. Our research team will first develop and characterize the relationship between the microsphere size and betamethasone release profiles to establish the feasibility of achieving long-term, controlled release to the inner ear (Aim 1). We will then determine the optimal microsphere immobilization strategy to enable RWM localization for a minimum of 14 days with minimal toxicity (Aim 2). The result will be microspheres that sustain a precise betamethasone dose and adhere to the RWM for sufficient time. After establishing the feasibility of this approach, we will, in Phase II, demonstrate our ability to precisely control the pharmacokinetic profile of inner ear betamethasone concentrations in small (mouse) and large (sheep) animal models. This PPF- enabled drug-delivery strategy addresses issues of dosage accuracy and long-term release. In addition, PPF- based encapsulation is highly adaptable and can serve as a transtympanic delivery platform for multiple drug classes. This unique strategy has significant potential to become the standard-of-care for treatment of SSNHL. PUBLIC HEALTH RELEVANCE: Current approaches to treat sudden sensorineural hearing loss (SSNHL) do not maintain inner ear drug concentrations within an appropriate therapeutic window for sufficient lengths of time to achieve therapeutic effect. A novel delivery system for long-term, controlled release of glucocorticoid steroids to the inner ear would constitute a dramatic improvement in SSNHL treatment options. Our proposed strategy uses Precision Particle Fabrication (PPF) to engineer glucocorticoid-loaded microspheres that are designed to remain localized to the round-window membrane of the inner ear and provide controlled and sustained release of the therapeutic throughout the treatment period.